Wheel bearing device and method of manufacturing the same

ABSTRACT

A wheel bearing device is provided to prevent loosening of a hub ring and an outer joint ring that are fitted together. An irregular portion treated with hardening is formed on a fit face of the hub ring on an inside periphery of which the outer joint member is fitted. A low hardness portion of the outer joint member formed with hardness lower than that of the irregular portion is expanded in diameter to make it bite into the irregular portion. In this way the hub ring and the outer joint ring are unitized together.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a wheel bearing device for supporting a wheelof an automobile and a method of manufacturing the same.

2. Description of the Related Art

Wheel bearing devices are broadly divided into two categories: those fordriving wheels, and those for driven wheels. For example, in a wheelbearing device for driving wheels, as FIG. 33 shows, a hub ring 100, abearing 200, and a constant velocity universal joint 400 are unitizedtogether. Further, of inner raceways of the bearing 200 in double rows,one of the inner raceways, or an inner raceway 270, is formed at the hubring 100, and the other inner raceway, or an inner raceway 280, isformed at an outer joint member 410 of the constant velocity universaljoint 400.

The hub ring 100 has a flange 140 for supporting a wheel, and the innerraceway 270 is formed at an outside periphery, near the flange 140, ofthe hub ring 100. The outer joint member 410 of the constant velocityuniversal joint 400 comprises a mouth portion 460 of a bowl shape and asolid stem portion 450, and is fitted on the hub ring 100 at the stemportion 450 through serration. A shoulder portion 470 of the outer jointmember 400 is in contact with an end face of the hub ring 100. The innerraceway 280 is formed at a portion of the outer joint member 410, or atan outside periphery of the mouth portion 460 near the stem portion 450.Outer raceways 240 in double rows facing to the inner raceways 270 and280 are formed at an inside periphery of an outer member 210 of thebearing 200. Further, rolling members 220 in double rows are assembledbetween the inner raceways 270 and 280 in double rows and the outerraceways 240 in double rows.

As indicated by numeral 450′, an end of the stem portion 450 projectingfrom the hub ring 100 in an axial direction is bent for swaging to jointogether the stem portion 450 and the hub ring 100. Further, the outermember 210 is fixed to a suspension device by a fixing portion 230formed in a flange shape facing outward at an outside periphery of theouter member 210, and a wheel is fixed to the flange 140 of the hub ring100.

Another example of a wheel bearing device is, as FIG. 34 shows, suchthat an inner ring 350 is fitted onto a small-diameter cylindricalportion 170 formed at the outside periphery of the hub ring 100. Knownas this type of wheel bearing device is such that an end of thesmall-diameter cylindrical portion 170 of the hub ring 100 projectingfrom the inner ring 350 in the axial direction is, as denoted by numeral170′, bent for swaging to join together the inner ring 350 and the hubring 100.

With the wheel bearing device described above, the bearing is generallygiven with preload, and precise preload control is made when assemblingthe bearing. In an automobile, however, large moment load is applied tothe bearing portion particularly when it turns. Therefore, in a methodwhere an end of the stem portion 450 of the outer joint member 410 (asshown in FIG. 33) or an end of the small-diameter cylindrical portion170 (as shown in FIG. 34) is bent and swaged, the swaged portion mayloosen owing to a reason such as spring-back at the swaged portion,resulting in a possible change in dimension between the inner racewaysin double rows and causing loss of preload.

SUMMARY OF THE INVENTION

Therefore, an object of the invention is to prevent loosening at aswaged portion.

Another object of the invention is to provide a method of manufacturinga wheel bearing device that can put preload to the inside of the bearingwhen swaging for joining, and can easily provide an appropriate amountof preload.

In order to achieve the objects described above, in a wheel bearingdevice according to the invention, a hub ring, a constant velocityuniversal joint, and a bearing are unitized together, the hub ring andan outer joint member of the constant velocity universal joint arefitted together, of inner raceways in double rows of the bearing, one ofthe inner raceways is formed at the hub ring while at the same time theother inner raceway is formed at the outer joint member. Further, ahardened irregular portion is formed at an outside-diameter side memberat a fit portion of the hub ring and the outer joint member, and also atthe same time, a low hardness portion having a hardness lower than thatof the irregular portion is provided at an inside-diameter side member.Then, the low hardness portion is expanded in diameter to make it biteinto the irregular portion, so that the hub ring and the outer jointmember are unitized together.

When the diameter of the low hardness portion is expanded to make itbite into the irregular portion as described above, joining strength isimproved in comparison with conventional swaging made by bending.Consequently, the hub ring and the outer joint member that are fittedtogether are prevented from loosening, and loss of preload can beavoided.

An effect similar to that described above is obtainable when a hardenedirregular portion is provided at the inside-diameter side member. Inthis case, the irregular portion itself is expanded in diameter to makeit bite into a mating face to which the irregular portion is fitted.However, if the irregular portion is excessively hardened, there is fearthat swaging cracks occur in a base material of the irregular portion asthe diameter is expanded. Therefore, the irregular portion cannot bemade too hard; Rockwell hardness (C scale, hereafter as well) of fromabout HRc 40 to 45 is the limit of the hardness. With such hardness asabove, however, the difference in hardness from its mating face offitting is only about HRc 20 to 25, and therefore the irregular portionmay be crushed as it bites into the mating face, causing possible lackin joining strength. As a countermeasure thereto, diameter-expansionallowance (extent of expansion toward an outside-diameter sides of theirregular portion may be increased. In this case, however, when once theirregular portion has bitten into its mating face to a certain depth,the fit portion starts to expands only toward an outside-diameter sideafterward without biting into the mating face, thereby producing poorjoining force.

On the other hand, when an member (an outside-diameter side member)having the irregular portion as described above and an member (aninside-diameter side member) to be expanded in diameter are arranged asseparate members, it is possible to sufficiently harden (to about HRc60, for example) the irregular portion. With the method described above,the irregular portion is prevented from being crushed in a swagingprocess and the member to be expanded in diameter can be provided with alow hardness portion having excellent ductility at the same time.Swaging cracks can be prevented from occurring through the expansion ofthis low hardness portion. Therefore, swaging is made into a deep depthbetween the hub ring and the outer joint member, so that sufficientjoining strength can be secured.

As an embodiment for fitting together the hub ring and the outer jointmember, there can be a case where the outside-diameter side member atthe fit portion is the hub ring and the inside-diameter side member isthe outer joint member (FIG. 1) or a case where the, outside-diameterside member at the fit portion is the outer joint member and theinside-diameter side member is the hub ring (FIG. 7).

Further, a wheel bearing device according to the invention comprises ahub ring and a bearing that are unitized together, the hub ring and aninner ring of the bearing are fitted together, and, of inner raceways indouble rows of the bearing, one of the inner raceways is formed at thehub ring while at the same time the other inner raceway is formed at theinner ring. In this wheel bearing device, moreover, a hardened irregularportion is formed at an outside-diameter side member at a fit portion ofthe hub ring and the inner bring, and also at the same time, a lowhardness portion having a hardness lower than that of the irregularportion is provided at an inside-diameter side member. The low hardnessportion is expanded to make it bite into the irregular portion, andthereby the hub ring and the inner ring are unitized.

In this case as well, the low hardness portion is expanded in diameterto make it bite into the irregular portion. Accordingly, joiningstrength higher than that obtainable in a conventional swaging method bybending is achieved and loss of preload can be avoided. Further, becausethe irregular portion and the member that is expanded in diameter areseparate members, the low hardness portion having excellent ductilitycan be provided at the member of which diameter is expanded while theirregular portion is being given sufficient hardness. Therefore, the lowhardness portion can be made to deeply bite into the irregular portion.

As an embodiment for fitting the hub ring and the inner ring together,there can be a case where the outside-diameter side member at the fitportion is the inner ring and the inside-diameter side member is the hubring (FIG. 8).

The wheel bearing device of the present invention can be used fordriving wheels when the outer joint member of the constant velocityuniversal joint is fitted to the inside periphery of the hub ring in amanner in which torque is transmittable (FIG. 19). In this case, a pilotportion that controls a clearance between the inside periphery of thehub ring and an outside periphery of the outer joint member is providednear a line extended from a line forming a contact angle of rollingmembers rolling on a inner raceway of the inner ring (FIG. 10). Thisarrangement prevents deformation of the fit portion of the hub ring andthe inner ring caused by load acting in a direction of the line thatforms the contact angles As a result, effect such as prevention ofbreakage of the hub ring and reduction in fretting wear between the hubring and the inner ring are obtained. Further, deformation of the innerraceway of the inner ring, caused by load in the direction of the linethat forms the contact angle, is prevented from occurring, so thateffect such as improvement of rolling life can be obtained. To obtainthe effects described above, it is preferable that a clearance width ofthe pilot portion is set at 0.4 mm or less.

When the low hardness portion is expanded in diameter at aninside-diameter side in an area including at least a part of either ofthe inner raceways, pressing force in a diameter expansion directionacts also on the outside-diameter side member. This pressing force isconverted by a contact angle of the rolling members into a component inan axial-direction, and the component acts in a direction to tighten thebearing clearance, giving preload to the bearing. In this case, preloadcontrol is facilitated because an amount of preload can be directly setat any value by the adjustment of pressing force acting in thediameter-expansion direction.

Hardening of the irregular portion described above is preferably made bya heat treatment using induction heating such as induction quenching(induction heat treatment). An induction heat treatment enables localheating as well as free selection of a depth of a hardened layer.Further, the treatment is advantageous in that it can be controlled soas not to significantly thermally affect areas other than the hardenedlayer, so that characteristics of a base material is maintainedunchanged.

Setting the difference in hardness between the irregular portion and thelow hardness portion at HRc 30 or more can securely prevent crushing ofthe irregular portion at the time of swaging.

Because the irregular portion is formed at an inside periphery of theoutside-diameter side member, working the portion with high accuracy isdifficult. Therefore, selection of a working method is an essentialpoint. In this case, the irregular portion can be effectively formedwith high accuracy with processes including broaching, particularly withhelical broaching repeated a plurality of times.

When the irregular portion is formed by grooves in a plurality of rowsmade to cross each other, fretting wear between the irregular portionand the low hardness portion in the axial direction or circumferentialdirection can be securely prevented.

The swaging described above is made by a swaging jig having a diameterlarger than that of an inside diameter of the inside-diameter sidemember. At this time, the swaging jig is made to slide on an insideperiphery of the inside-diameter side member to expand in diameter thelow hardness portion. In this case, the low hardness portion ispreferably expanded in diameter by the swaging jig while theinside-diameter side member is being pushed into a direction of reducingan axial bearing clearance. With this method, because pressing force inthe axial direction is given to the inside-diameter side member by theswaging jig, the inside-diameter side member and the outside-diameterside member can be joined by swaging while the axial bearing clearanceis being reduced. Therefore, a necessary and sufficient amount ofpreload can be put in a simple process and preload control isfacilitated.

Conventionally, as shown in FIG. 35, a stem portion 450 of the outerjoint member 410 is first pressed into the inside of the hub ring 100.After that, with a bottom portion of the mouth portion 460 of the outerjoint member 410 being supported by a receive member 520, a swaging jig540, having a larger diameter than an inside diameter of the stemportion 450 of the outer joint member 410, is pressed into the inside ofthe stem portion 450 in the direction of the arrow to partly expand adiameter of the stem portion 450 (Japanese Patent Laid-Open PublicationNo. 2001-18605). By doing so, pressing force in the axial direction ofthe swaging jig 540 is directly supported by the receive member 540without allowing the pressing force to pass through the hub ring 100 atan outside-diameter side. With this method, however, a clearance T isproduced after swaging at a butt portion between an end face of the hubring 100 and a shoulder face 470 of the outer joint member 410 (see FIG.36), and the clearance T may cause loss of preload, possibly affectingbearing rigidity or bearing endurance life.

On the other hand, the method according to the invention is, as anexample in FIG. 22, a method of manufacturing a wheel bearing devicecomprising: an outer joint member 21 having outer raceways 24 in doublerows on its inside periphery; an inner member 29 having inner raceways27 and 28 in double rows facing to the outer raceways, aninside-diameter side member 61, and an outside-diameter side member 63fitted onto the inside-diameter side member with an irregular portion 31interposed in between; and rolling members 22 in double rows disposedbetween the outer raceways and inner raceways. With this method, theinside-diameter side member 61 is at least partly expanded in diameterby a swaging jig 54 pushed into the inside of the inside-diameter sidemember 61, so that the irregular portion 31 bites into its opposing faceto join together by swaging the inside-diameter side member 61 and theoutside-diameter side member 63. At this time, the inside-diameter sidemember 61 is expanded in diameter while being pressed by the swaging jig54 toward axially one side with the inside-diameter side member 61 beingmade butt against axially the other side of the outside-diameter sidemember 63 and the outside-diameter side member 63 at the axially oneside being supported by the receive member 52.

When the inside-diameter side member 61 is pressed toward the axiallyone side by the swaging jig 54, the outside-diameter side member 63butting against the inside-diameter side member 61 is in turn pressedand pushed in to the same direction. In this Process, theoutside-diameter side member 63 at the axially one side is supported bythe receive member 52 and prevented from moving toward the direction ofthe axially one side. In other words, a pressing force in an axialdirection of the swaging jig 54 is received and supported by the receivemember 52 after passing through the inside-diameter side member 61 andthen the outside-diameter side member 63. Consequently, clearancebetween both end faces of the inside-diameter side member 61 and theoutside-diameter side member 63 is tightened at a butt portion 70 wherethe two members butt against each other, and compression strain remainsat and around the butt portion 70. As a result, a distance L, indicatedin FIG. 23(A), between the inner raceways 27 and 28 before the swagingis decreased by an amount of compression strain δ, indicated in FIG.23(B), after the swaging (to become L-δ). Therefore, through the settingof this δ at an appropriate value, a desired amount of preload can begiven to the bearing with an axial bearing clearance being negative.After swaging, the inside-diameter side member 61 and theoutside-diameter side member 63 are solidly joined together withoutloosening through the biting of the irregular portion 31 into theopposing face 36. Consequently residual compression strain does notdisappear and initial preload is steadily maintained for a long period.

In this case, the amount of the compression strain δ is dependent on apush-in force F of the swaging jig 54 (see FIG. 22) and also on rigidityof the inside-diameter side member 61 and outside-diameter side member63, or more specifically rigidity at and around the butt portion 70 ofboth the members 61 and 63. Therefore, preload can be set in a mostappropriate range by controlling the push-in force F.

To smoothly carry out the process described above, an outside diameterφA of the swaging jig 54, an inside diameter φB of the portion 34 to beswaged of the inside-diameter side member 61, and an inside diameter φCof the inside-diameter side member 61 excluding the portion 34 to beswaged are set at the relationship of φC>φA>φB.

The swaging jig 54 can also be of an expandable/reducible structure, Bydoing so, even the portion 34 to be swaged located at an opening side ofa bottomed cylindrical member (such as the outer joint member 41blocking a bottom of the mouth portion 46) as shown in FIG. 29 can alsobe swaged for joining. Specifically, the swaging jig 54 reduced to adiameter which is smaller than an inside diameter of the portion 34 tobe swaged is inserted into the inside of the inside-diameter side member41 (outer joint member) up to a position beyond the portion 34 to beswaged. Then, the swaging jig 54 is expanded in diameter to a dimensionlarger than that of the portion 34 to be swaged, and then the swagingjig 54 is drawn in the direction opposite to the insertion. Thus, withthe same effect as described above, the inside-diameter side member 41and the outside-diameter side member 10 (hub ring) can be securelyswaged for joining,

The swaging jig can be, for example, composed in an expandable/reduciblestructure by taper-fitting of a divided punch divided in acircumferential direction and an insertion member slidably inserted intothe inside of the divided punch.

The inside-diameter side member can be joined by swaging to theoutside-diameter side member provided with the inner raceway. It canalso be joined by swaging to the outside-diameter side member 71 (seeFIG. 32) that is not provided with an inner raceway. In the latter case,deformation of the inner raceway cause by swaging can be prevented fromoccurring.

The nature, principle, and utility of the invention will become moreapparent from the following detailed description when read inconjunction with the accompanying drawings in which like parts aredesignated by like reference numerals or characters.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings:

FIG. 1 is a longitudinal cross sectional view of a wheel bearing deviceaccording to an embodiment of the invention;

FIGS. 2(A) and 2(B) are a front view and longitudinal cross sectionalview, respectively, of a hub ring showing a formation process of anirregular portion;

FIGS. 3(A) and 3(B) are longitudinal cross sectional views of a hub ringshowing a formation process of an irregular portion;

FIGS. 4(A) and 4(B) are enlarged longitudinal cross sectional views ofirregular portions;

FIG. 5 is a longitudinal cross sectional view showing a swaging process;

FIG. 6 is an enlarged longitudinal cross sectional view of an essentialpart in FIG. 5.

FIG. 7 is a longitudinal cross sectional view showing a wheel bearingdevice according to another embodiment of the present invention;

FIG. 8 is a longitudinal cross sectional view showing a wheel bearingdevice according to another embodiment;

FIGS. 9(A), 9(B), and 9(C) are unfolded plan views of examples of theirregular portion;

FIG. 10 is an enlarged cross sectional view of an inboard essential partof the wheel bearing device shown in FIG. 8;

FIG. 11 is a side view of a swaging jig;

FIGS. 12(A) and 12(B) are a transverse cross sectional view and a sideview of a swaging jig, respectively;

FIG. 13 is a longitudinal cross sectional view showing a swaging processusing the swaging jig shown in FIG. 11;

FIG. 14 is a longitudinal cross sectional view showing a swaging processusing the swaging jig shown in FIG. 11;

FIG. 15 is a longitudinal cross sectional view showing a swaging processusing the swaging jig shown in FIGS. 12(A) and 12(B);

FIG. 16 is a longitudinal cross sectional view showing a swaging processusing the swaging jig indicated in FIGS. 12(A) and 12(B);

FIG. 17 is a longitudinal cross sectional view showing a swaging processusing the swaging jig indicated in FIGS. 12(A) and 12(B);

FIG. 18 is a longitudinal cross sectional view showing a swaging processusing the swaging jig indicated in FIGS. 12(A) and 12(B);

FIG. 19 is a longitudinal cross sectional view of a wheel bearing devicewith an outer joint member assembled thereto;

FIG. 20 is a longitudinal cross sectional view of another embodiment ofloosening prevention means;

FIG. 21 is a longitudinal cross sectional view of still anotherembodiment of loosening prevention means;

FIG. 22 is an enlarged cross sectional view of an essential partillustrating a method for manufacturing a wheel bearing device accordingto the invention;

FIGS. 23(A) and 23(B) are longitudinal cross sectional views of a wheelbearing device before and after joining by swaging, respectively;

FIG. 24 is a longitudinal cross sectional view of a wheel bearingdevice;

FIG. 25 is an enlarged longitudinal cross sectional view of an essentialpart shown in FIG. 24;

FIG. 26 is a longitudinal cross sectional view showing another exampleof a wheel bearing device;

FIG. 27 is a longitudinal cross sectional view showing still anotherexample of a wheel bearing device;

FIG. 28 is a longitudinal cross sectional view showing another exampleof a wheel bearing device for a driving wheel

FIG. 29 is a longitudinal cross sectional view illustrating a method formanufacturing a wheel bearing device for a driving wheel;

FIG. 30 is a transverse cross sectional view of a swaging jig that isconstituted to be expandable and reducible in diameter;

FIG. 31 is a longitudinal cross sectional view of the swaging jig shownin FIG. 30;

FIG. 32 is a longitudinal cross sectional view of another example of awheel bearing device;

FIG. 33 is a longitudinal cross sectional view of a conventional wheelbearing device;

FIG. 34 is a longitudinal cross sectional view of a conventional wheelbearing device;

FIG. 35 is a longitudinal cross sectional view showing a conventionalmethod of manufacturing a wheel bearing device; and

FIG. 36 is a longitudinal cross sectional view of a conventional wheelbearing device.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the invention will be described below referring to FIGS.1 to 32.

FIG. 1 shows a wheel bearing device for a driving wheel according to theinvention. The wheel bearing device is composed of a hub ring 10, abearing 20, and a constant velocity universal joint 40 in a unitizedform. In the description below, a side toward an outside of a vehicle ina state where the wheel bearing device is fixed to the vehicle is calledthe “outboard side”, and a side toward an center of the vehicle iscalled the “inboard side”.

At an outboard end portion of the hub ring 10 is provided with a flange14 for fixing a wheel (not shown), and hub bolts 15 (see FIGS. 7, 8 andothers) are studded at the flange 14 at equal intervals in acircumferential direction for fixing a wheel disk. An outboard innerraceway 27 is formed on an outside periphery of the hub ring 10 at aposition more inboard than the flange 14. The hub ring 10 is formed in ahollow shape having a through-hole prepared in an axial direction at itsaxis portion.

The constant velocity universal joint 40 transmits torque from a driveshaft to the outer joint member 41 through an inner joint member 42 andtorque transmission balls 43 (see FIG. 7). A plurality of track grooves41 a are formed at an inside periphery of the outer joint member 41. Aplurality of ball tracks are formed jointly by the track grooves 41 aand a plurality of track grooves 42 a provided on an outside peripheryof the inner joint member 42, and the constant velocity universal joint40 is formed by the torque transmission balls 43 disposed at each balltrack. Each of the torque transmission balls 43 is retained on the sameplane by a cage 44. The outer joint member 41 comprises a stem portion45 and a mouth portion 46, and is fitted to the inside periphery of thehub ring 10 at the stem portion 45. An inboard-side inner raceway 28 isformed at an outside periphery, at a position near a shoulder face 47 ofthe mouth portion 46. The shoulder face 47 of the mouth portion 46contacts an inboard end face of the hub ring 10 to position the hub ring10 and the outer joint member 41 in the axial direction, and a dimensionbetween the inner raceways 27 and 28 is defined. The stem portion 45 hasa hollow shape provided with a through-hole 48 in the axial directionconnected with a bottom of the mouth portion 46 of a bowl shape.

The bearing 20 includes an outer member 21 and rolling members 22 indouble rows. The outer member 21 is provided with a flange 23 for use infixation of the bearing device on a vehicle body (not shown) and isformed on its inside periphery with outer raceways 24 in double rows forthe rolling members 22 in double rows. The rolling members 22 areassembled between the outer raceways 24 in double rows of the outermember 21 and the inner raceways 27 and 28, in which the inner racewaysare provided respectively at the hub ring 10 and the outer joint member41. Shown in the figure is a case where a double-row angular ballbearing using balls is used as the rolling member 22; however, adouble-row conical roller bearing using conical rollers as the rollingmembers may be adopted for wheel bearing devices for heavy automobiles.Seals 25 and 26 are installed at opening portions of both ends of theouter member 21 to prevent grease filled inside the bearing from leakingand water and foreign matter entering from outside.

An irregular portion 31 with projections and depressions is formed on afit face 16 at an inside periphery of the hub ring 10 The irregularportion 31 is formed at at least a part of the fit face 16 of the hubring 10, or, for example, at an outboard end portion of the fit face 16of the hub ring 10. A part other than the irregular portion 31 of thefit face 16 is formed in a cylindrical shape that close-fits to acylindrical outside periphery of the stem portion 45.

Projections and depressions of the irregular portion 31 can be of anypattern of a shape. They can be formed, for example, in a screw-threadpattern, a serration (including spline) pattern or a diamond-knurlingpattern with grooves in a plurality of parallel rows made to cross eachother. Among others, the diamond knurling is particularly effective forpreventing fretting wear (particularly, fretting wear in the axial andcircumferential directions) after swaging, which will be describedbelow.

In FIGS. 2(A) and 2(B), the irregular portion 31 having adiamond-knurling pattern is formed by a process including broaching.Specifically, as shown in FIG. 2(A), a plurality of grooves 31 a 1 inthe axial direction are first formed on the fit face 16 at the insideperiphery of the hub ring 10, After that, as in FIG. 2(B), a pluralityof grooves 31 a 2 crossing at right angle to the grooves 31 a 1 areformed by turning in the circumferential direction. The grooves 31 a 1in the axial direction and the grooves 31 a 2 in the circumferentialdirection may be formed in any order; the grooves 31 a 2 may be firstformed in the order reversed from that described above. Besides theirregular portion 31 of a diamond-knurling pattern can also be formed byhelical broaching applied a plurality of times as shown in FIGS. 3(A)and 3(B). That is, as shown in FIG. 3(A), first helical grooves 31 b 1are formed on the fit face 16 at the inside periphery of the hub ring 10by helical broaching in the axial direction. Then, second helicalgrooves 31 b 2 are formed by second helical broaching, appliedsymmetrically to the first broaching with respect to an axis of the hubring 10, to finally form the irregular portion 31 of a diamond-knurlingpattern.

FIGS. 4(A) and 4(B) show enlarged cross sectional views taken in theaxial direction of the irregular portion 31 formed in a manner describedabove. As the figures illustrate, projection portions 32 of theirregular portion 31 are formed in a pointed-end shape to secureexcellent bite-in capability, and groove portions 31 a 2, 31 b 1, and 31b 2 are formed, for example, in a shape of a circular-arc [FIG. 4(A)] ora triangle [FIG. 4(B)] in the cross section.

The irregular portion 31 formed in this way is hardened up toapproximately HRc 60 by a heat treatment. Induction quenching issuitable as the heat treatment for this purpose, because it enableslocal heating, provides free selection of a depth of a hardened-layer,and gives less thermal affect to areas other than a hardened layer sothat characteristics of a base material can be maintained. A hardenedlayer created by a heat treatment is formed, as dotted patterns indicatein FIG. 1, not only in an area (inside periphery of the hub ring 10)including the irregular portion 31 of the hub ring 10, but also in anarea (outside periphery of the hub ring 10) including the inner raceway27 of the hub ring 10. When both the hardened layers are interruptedlyformed as indicated in the figure, the hub ring 10 is less likely tocrack.

As FIG. 1 shows, a low hardness portion 33 having hardness lower thanthat of the irregular portion 31 is formed at the outside periphery ofthe stem portion 45 of the outer joint member 41. It is enough if thelow hardness portion 33 is formed at, of an outside periphery of thestem portion 45, at least in an area facing to the irregular portion 31,and other areas at the outside periphery of the stem portion 45 may behardened with a treatment such as a heat treatment. The low hardnessportion 33 may be formed as an un-heat-treated portion where a basematerial is left un-heat-treated through the omission of a heattreatment. Further, it can also be formed by a hardening treatment toharden it to ranges that do not exceed hardness of the irregular portion31. In this case, the difference in hardness between the irregularportion 31 and the low hardness portion 33 is preferably set to HRc 30or more. With this arrangement, the irregular portion 31 can smoothlybite into the low hardness portion 33 of the outer joint member 41without being crushed at the time of swaging.

After the irregular portion 31 is treated for hardening, the stemportion 45 of the outer joint member 41 is fitted to the insideperiphery of the hub ring 10. Further, the low hardness portion 33 atthe outside periphery of the stem portion 45 is expanded in diametertoward an outside-diameter side from an inside-diameter side. Then, thelow hardness portion 33 bites into the irregular portion 31 toplastically join the hub ring 10 and the outer joint member 41 while atthe same time a dimension between the inner raceways 27 and 28 isdefined and desired preload is put to the inside of the bearing 20. Thehub ring 10 and the outer joint member 41, which are plastically joinedtogether, form an inner member 29 having the inner raceways 27 and 28 indouble rows.

According to the invention, the low hardness portion 33 of the stemportion 45 bites, when swaged, from a radial direction into theirregular portion 31 at the inside periphery of the hub ring 10.Therefore, more solid joining is obtainable than in a conventionalswaging method using bending, and therefore loosening at the swagedportion is-prevented. As described above, the irregular portion 31 isnot to be easily crushed because of its high hardness. Further, becausethe low hardness portion 33 expanded in diameter has hardness lower thanthat of the irregular portion 31 and has excellent ductility, swagingcracks are less likely to occur even larger diameter-expansion allowanceis provided at the low hardness portion. Thus, the irregular portion 31can be made to deeply bite into the low hardness portion 33, and thejoining strength of the hub ring 10 and the outer joint member 41 isgreatly improved.

Swaging can be made by, for example as shown in FIG. 5, inserting aswaging jig 54 (punch) into a through-hole 48 inside of the stem portion45 of the outer joint member 41. That is, the stem portion 45 of theouter joint member 41 is first fitted into the inside periphery of thehub ring 10. That is, the swaging jig 54 having an outside diameterlarger than an inside diameter of the through-hole 48 of the stemportion 45 is pushed into the through-hole 48 with an end face of theflange 14 of the hub ring 10 being supported by a back-up jig 52(receive member) and an outboard-side outside diameter portion of thehub ring 10 being restrained in position. Then, the low hardness portion33 is expanded in diameter to the outside-diameter side from theinside-diameter side. A portion swaged with this diameter expansion, ora portion to be swaged, is indicated with numeral 34.

FIG. 7 shows that, at a fit portion of the hub ring 10 and the outerjoint member 41, the hub ring 10 is disposed at an inside-diameter side,oppositely from the case shown in FIG. 1, while at the same time theouter joint member 41 is disposed at an outside-diameter side. In thiscase, a portion 34 to be swaged is a small-diameter cylindrical portionof the hub ring 10 and is provided at an inside-diameter side of theinboard inner raceway 28. The hardened irregular portion 31 is formed atan inside periphery of the stem portion 45 of the outer joint member 41,and the low hardness portion 33 is formed at the outside periphery ofthe hub ring 10 facing to the irregular portion 31 (x marks indicate theareas where the irregular portion 31 is formed. So does the same in thedescription below.). In this case as well, the portion 34 to be swagedof the hub ring 10 is expanded in diameter for swaging from aninside-diameter side toward an outside-diameter side so as to expand adiameter of the low hardness portion 33. Thus the low hardness portion33 can be made to deeply bite into the irregular portion 31, so that thehub ring 10 and the outer joint member 41 can be firmly joined together.

Hardened layers (indicated with a dotted pattern) prepared by a heattreatment is formed not only at areas (inside periphery of the stemportion 45) including the irregular portion 31, but also formed at areas(outside, periphery of the stem portion 45) including the inboard innerraceways 28. In this case, same as the embodiment in FIG. 1, the outerjoint member 41 can be made to be less likely to crack when both thehardened layers are interruptedly formed.

FIG. 8 shows an embodiment where the hub ring 10 and the bearing 20 areunitized together. The hub ring 10 is of a hollow shape having athrough-hole 19, and a small-diameter cylindrical portion 17 is formedat an inboard end portion of the hub ring 10. The inner member 29 havingthe inner raceways 27 and 28 in double rows is formed by fitting aninner ring 35 of the bearing 20 to an outside periphery of thesmall-diameter cylindrical portion 17. Of the inner raceways 27 and 28in double rows, the outboard inner raceway 27 is formed at the outsideperiphery of the hub ring 10 at more inboard than the flange 14, and theinboard inner raceway 28 is formed at an outside periphery of the innerring 35. An outboard end face of the inner ring 35 contacts the shoulderface 18 of the hub ring 10, thereby defining the dimension between theinner raceways 27 and 28 and giving preload to the inside of thebearing. Shown as an example in the figure are balls having a contactangle (indicated with dash-dotted lines) disposed between the outerraceways 24 and the inner raceways 27 and 28 in double rows.

The irregular portion 31 and the low hardness portion 33 that aredescribed above are formed at a fit portion of the hub ring 10 and theinner ring 35. More specifically, the irregular portion 31 is formed Atan inside periphery of the inner ring 35 located at an outside-diameterside of the fit portion, and the low hardness portion 33 is formed atthe outside periphery of the hub ring 10 located at an inside-diameterside of the fit portion. The irregular portion 31 may be formed, forexample, only with grooves in a circumferential direction as shown inFIG. 9(A) or may be formed in a diamond-knurling pattern with grooves ina plurality of rows that are made to cross each other at right angles asshown in FIGS. 9(B) and 9(C). FIG. 9(B) shows inclined grooves, and FIG.9(C) shows grooves in axial and circumferential directions. It may alsobe formed in a screw-thread pattern or a serration (including spline)pattern besides those described above.

The hardening treatment described above is applied to the irregularportion 31. Further, the low hardness portion 33 is formed by omissionof a heat treatment or formed by hardening of the portion for hardnessnot exceeding the hardness of the irregular portion 31. In this case,the difference in hardness between the irregular portion 31 and the lowhardness portion 33 is preferably set to HRc 30 or more. Same as theembodiment in FIG. 1, when the portion 34 to be swaged of the hub ring10 is swaged for expanding in diameter the low hardness portion 33, thelow hardness portion 33 bites into the irregular portion 31. Thus thehub ring 10 and the inner ring 35 are plastically joined as aconsequence, preventing loosening at the swaged portion from occurring.

In the embodiments in FIGS. 7 and 8, swaging is made at aninside-diameter portion of the inboard inner raceway 28 as shown in FIG.10 (illustrated corresponding to FIG. 8). When the low hardness portion33 is expanded in diameter at this position, diameter-expanding forcecauses a component force in the axial direction (direction from theinboard side toward the outboard side) within the bearing because of acontact angle of the rolling members 22. Therefore, preload can be putto the bearing at the sate time when the hub ring 10 and the inner ring35 are plastically joined. In this case, preload control is facilitatedbecause an amount of preload is directly adjustable through the changeof a diameter-expansion force. Swaging is not necessarily made at aninside-diameter side that covers the entire area of the inner raceway 28as long as solid plastic joining is obtainable and preload can beapplied. It is fine in this case if at least a part of theinside-diameter side portion of the inner raceway 28 is included in thearea to be swaged.

Swaging of the low hardness portion 33 by the expansion of its diametercan be made with the swaging jig 54, having a diameter larger than aninside diameter of the hub ring 10 at the fit portion, made to slideinside the hub ring 10 in the same way as in FIG. 5. FIGS. 11, and 12(A)and 12(B) show examples of the swaging jig 54; FIG. 11 shows the swagingjig 54 having a certain outside-diameter dimension; and FIGS. 12(A) and12(B), the swaging jig 54 having an adjustable outside diameter. Theswaging jig 54 of an adjustable type shown in FIGS. 12(A) and 12(B) hasa divided punch 55 divided at a plurality of positions in acircumferential direction, and it expanded or reduced in diameter when amandrel 56 (insertion member) is inserted into or drawn from its inside.

Swaging by diameter expansion using the swaging jig 54 shown in FIG. 11is achieved by push of the swaging jig 54 into the through-hole 19 ofthe hub ring 10 from an inboard end face of the inner ring 35. At thistime, an outboard end face of the hub ring 10 is supported by a supportmember 53 while the inboard end face of the inner ring 35 is restrainedin position by the back-up jig 52. On the other hand, in swaging bydiameter expansion using the swaging jig 54 of an adjustable type shownin FIGS. 12(A) and 12(B), the swaging jig 54 with a reduced diameter isfirst inserted into the through-hole 19 of the hub ring 10 from inboardas shown in FIGS. 15 and 16. Then, as FIG. 17 shows, the mandrel 56 isinserted into the inside of the divided-punch 55 to expand in diameterthe swaging jig 54 so that an outside periphery of the swaging jig 54 ispressed against an inside periphery of the small-diameter cylindricalportion 17 (portion 34 to be swaged) of the hub ring 10. With this statebeing held, the swaging jig 54 is drawn out to make swaging. Besides, asshown in FIG. 18, the portion 34 to be swaged can also be swaged byinserting the swaging jig 54 of an adjustable type from outboard intothe inside of the hub ring 10.

In the processes shown in FIGS. 13 to 17, the swaging jig 54 can beinserted into the through-hole 19 from inboard. This is enabled becausethe inside diameter of the small-diameter cylindrical portion 17(portion 34 to be swaged) is larger than that of the serrated portion 37formed at an outboard inside periphery of the small-diameter cylindricalportion 17. However, when the inside diameter of the portion 34 to beswayed is smaller than that of the serrated portion 37, the swaging jig54 shown in FIG. 11 can also be inserted into the inside of the portion34 to be swaged from outboard for swaging.

In wheel bearing devices shown in FIGS. 8 and 18, the outer joint member41 of the constant velocity universal joint 40 is inserted into theinside of the hub ring 10 as shown in FIG. 19. More specifically, thestem portion 45 of the outer joint member 41 is inserted into thethrough-hole 19 of the hub ring 10 and the serrated portion 37 formed atthe inside periphery of the hub ring 10 and a serrated portion (numeralnot given) formed at the outside periphery of the stem portion 45 arefitted together. Thus the hub ring 10 and the outer joint member 41 arejoined together in a manner where torque is transmittable. In this typeof wheel bearing device, as described above, both loosening preventionand preload control of the inner ring 35 are provided by swaging throughexpansion in diameter of the low hardness portion 33. Therefore, it isenough to fix the outer joint member 41 to the hub ring 10 by simpleloosening prevention means 38 such as a circlip that is enough andsufficient to prevent the hub ring 10 from loosening. A socket-head boltshown in FIG. 20 or a nut shown in FIG. 21 may be used as otherloosening prevention means 38.

As shown in FIG. 10, a pilot portion P is formed near a line extendedfrom a line (indicated with a dash-dotted line) forming a contact angleof the inboard rolling members 22. The-pilot portion P functions to makeclose-fit together the outside periphery of the hub ring 10 and theinside periphery of the inner ring 35, while it functions to limit aclearance S in a radial direction between the inside periphery of thehub ring 10 and the outside periphery of the outer joint member 41 belowa certain value. A large clearance at a fit face between the outsideperiphery of the hub ring 10 and the inside periphery of the hub ring 35may cause fretting wear between the hub ring 10 and the inner ring 35.However, fretting wear between the hub ring 10 and the inner ring 35 isreduced when the outside periphery of the hub ring 10 and the insideperiphery of the inner ring 35 are close-fitted together. Also, when aclearance S between the inside periphery of the hub ring 10 and theoutside periphery of the outer joint member 41 is excessively large,loads in the direction of a line forming a contact angle may deform thesmall-diameter cylindrical portion 17 of the hub ring 10, and furtherdeforms the inner raceway 28. This in turn may cause harmful effectssuch as fretting wear between the hub ring 10 and the inner ring 35,decreased rolling life and rise in temperature of the inner raceway 28.As described above, however, with the clearance S of the pilot portion Plimited below a certain value, this kind of deformation by loads in thedirection of a line forming a contact angle Can be prevented and life ofa wheel bearing device is improved. In order to obtain the effectdescribed above, the clearance S of the pilot portion is preferably setto 0.4 mm or less.

Further, when the inside periphery of the hub ring 10 and the outsideperiphery of the outer joint member 41 are closed-fitted together tomake the clearance S between them “zero,” relative run-out between theouter joint member 41 and the hub ring 10 caused by the clearance S inthe rotation of the hub ring 10 is prevented from occurring. Thisclose-fit can be realized depending on the direction in which the outerjoint member 41 having an outside diameter larger than the insidediameter of the hub ring 10 is inserted into the inside of the hub ring10.

The wheel bearing device shown in FIG. 24 is composed of an outer member21 having the outer raceways 24 in double rows at its inside periphery,an inner member 29 having at its outside periphery the inner raceways 27and 28 in double rows disposed at the inside diameter side of the outermember 21 and facing to the outer raceways 24, and the rolling members22 in double rows disposed between the outer raceways 24 and the innerraceways 27 and 28. Formed at the outer member 21 is the flange 23 to befixed to a wheel or a vehicle body (FIG. 24 shows an example when theflange 23 is fixed to a vehicle body side.).

The inner member 29 shown in the figure as an example is composed of afirst inner ring 61 having the outboard inner raceway 27 and a secondinner ring 63 having the inboard inner raceway 28. An inboard portion ofthe first inner ring 61 is formed in a small-diameter cylindrical shape,and the second inner ring 63 is fitted onto this small-diametercylindrical portion 62. Accordingly, in this embodiment, the first innerring 61 is an inside-diameter side member and the second inner ring 63is an outside diameter side member at the fit portion.

Both the inner rings 61 and 63 are joined by swaging that is made by theexpansion in diameter of the portion 34 to be swaged located at aninboard end portion of the small-diameter cylindrical portion 62. Theirregular portion 31 is disposed at the fit portion of the first innerring 61 and the second inner ring 63. Therefore, when the diameter ofthe portion 34 to be swaged is expanded, the irregular portion 31 bitesinto an opposing face 36 so as to join both inner rings 24 and 25 byswaging in a manner where torque is transmittable. At this time, theirregular portion 31 is preferably formed on the inside periphery of thesecond inner ring 63 and is treated for hardening as shown in FIG. 25 sothat swaging cracks are prevented from being produced and that bite-incapability is improved. In this case, the outside periphery of the firstinner ring 6 l facing to the irregular portion 31 is made as a lowhardness portion with hardness lower than that of the irregular portion31. When no particular problem exists, the irregular portion 31 may beformed on the outside periphery of the first inner ring 61.

In this embodiment, differently from that shown in FIG. 8, the portion34 to be swaged of the first inner ring 61 is formed in areas outsidethe inside-diameter portion of the inner raceways 27 and 28, or, asillustrated in the figure, at more inboard than the inboard innerraceway 28, so that deformation of the inner raceway 28 caused byswaging is prevented.

As shown in FIGS. 22 and 24, an end face of one side (outboard side inthis embodiment) in an axial direction of the second inner ring 63 isbutted against a shoulder face 64 of the first inner ring 61(inside-diameter side member). Here, when the swaging jig 54 insertedinto the inside of the first inner ring 61 is pushed into the other side(inboard side in this embodiment) in the axial direction, the portion 34to be swaged is pushed in toward the other side in the axial direction,and further the first inner ring 61 is pushed in toward the samedirection. Then the second inner ring 63 butted in the axial directionagainst the first inner ring 61 is also pushed in toward the samedirection. To prevent the movement of the second inner ring 63 towardthe other side in the axial direction resulted from the effect describedabove, the end face of the other side in the axial direction of thesecond inner ring 63 is supported by the receive member 52.

As a result of the procedure described above, a clearance between theend faces of the first inner ring 61 and second inner ring 63 istightened at a butt portion 70 as the swaging jig 54 is pushed in, andcompression strain [cross-hatched portion in FIG. 23(B)] remains at bothsides of the butt portion 70 in the axial direction. Therefore, preloadcan be put to the bearing with an axial bearing clearance beingnegative. Thus it is possible to complete preload setting simultaneouslywhen connection by swaging is completed. In this case, an amount ofcompression strain δ is determined by a push-in force F of the swagingjig 54, and rigidity of a portion at and around the butt portion 70 ofthe first inner ring 61 and second inner ring 63. Therefore, preload canbe set to a most appropriate range by controlling the push-in force F.

In this swaging process, the swaging jig 54 is inserted up to an inboardopening portion from an outboard opening portion of the first inner ring61. For this purpose, to facilitate smooth insertion of the swaging jig54, an inside diameter φC of the first inner ring 61 in an area up tothe portion 34 to be swaged must be larger than an outside diameter φAof a maximum outside-diameter portion 57 (cross-hatched in the figure,and so is the same with FIG. 10) of the swaging jig 54 (φC>φA). Further,in order to securely push the swaging jig 54 against the portion 34 tobe swaged, the outside diameter φA of the maximum outside-diameterportion 57 of the swaging jig 54 must be larger than an inside diameterφB of the portion 34 to be swaged (φA>φB). Accordingly, the insidediameter φC of the first inner ring 61 excluding the portion 34 to beswaged, the outside diameter φA of the maximum outside-diameter portion57 of the swaging jig 54, and the inside diameter φB of the portion 34to be swaged must fulfill the relationship of φC>φA>φB.

FIG. 26 shows a wheel bearing device in which, same as in FIG. 8, thehub ring 10 and the bearing 20 are unitized together. In thisembodiment, the portion 34 to be swaged is disposed at more inboard thanthe inner raceway 28, which is different from the embodiment in FIG. 8.However, other constitutions are the same as those of the embodiment inFIG. 8 and therefore repeated descriptions are omitted. The hub ring 10as the inside-diameter side member and the inner ring 35 as theoutside-diameter side member are joined by swaging. To make the swaging,the swaging jig 54 is inserted into the hub ring 10 to expand indiameter the portion 34 to be swaged. Because an end face of one side(inboard side in this embodiment) in an axial direction of the innerring 37 is butted against the shoulder face 18 of the hub ring 10, anappropriate amount of preload can be put to the bearing by tightening ofa clearance at the butt portion 70 between the hub ring 10 and the innerring 35. Specifically, this is done by pushing in the swaging jig 54toward the other side in an axial direction of the inner ring 35 with anend face of the other side (inboard side) being supported by the receivemember 52.

FIG. 27 shows an embodiment where, oppositely from the embodiment inFIG. 26, the hub ring 36 is fitted onto an small-diameter cylindricalportion 35 a of the inner ring 35 so that the inner ring 35 is theinside-diameter side member and the hub ring 10 is the outside-diameterside member. In the same ways as above, axially one side (inboard sidein this embodiment) of the hub ring 10 is butted against the shoulderface 30 of the inner ring 35, and at the same time, the swaging jig 54is pushed into the inside of the hub ring 10 toward the axially otherside of the hub ring 10 with an end race of the axially other side ofthe hub ring 10 being supported by the receive member 52. Then, theportion 34 to be swaged of the hub ring 10 is expanded in diameter forswaging to join it to the inner ring 35. At this time, compressionstrain is produced at and around the butt portion 70 between the hubring 10 and the inner ring 35 so as to give an appropriate amount ofpreload to the inside of the bearing.

The swaging process described above can also be applied to a wheelbearing device (see FIGS. 1 and 7) for a driving wheel in which the hubring 10, the bearing 20, and the constant velocity universal joint 40are unitized together. For example, in the wheel bearing device shown inFIG. 1, axially one side (inboard side in this embodiment) of the hubring 10 as the outside-diameter side member is butted against a shoulderface 47 of the outer joint member 41 as the inside diameter side memberas shown in FIG. 5. Then, the outer joint member 41 is expanded indiameter while being pressed by the swaging jig 54 toward the axiallyother side with an end face of the axially other side (outboard side) ofthe hub ring 10 being supported by the receive member 52. In this case,preload is put to the bearing because a force in the axial direction, ora force as a component of working force, acting in a direction(direction in which the inboard inner raceway 28 approaches the outboardinner raceway 27) to reduce an axial bearing clearance acts on the outerjoint member 41 as shown in FIG. 6. On the other hand, in the wheelbearing device in FIG. 7, the hub ring 10 is expanded in diameter whilebeing pressed by the swaging jig 54 toward the axially other side with ashoulder face 18 of the hub ring 10 as the inside-diameter side memberbeing butted against axially one side (outboard side in this embodiment)of the outer joint member 41 as the outside-diameter side member andwith the axially other side (inboard side) of the outer joint member 41being supported by the receive member 52.

FIG. 28 shows another embodiment of a bearing device (see FIG. 7) for adriving wheel having the outer joint member 45 fitted onto the hub ring10, in which the inboard inner raceway 27 is formed at an memberdifferent from the hub ring 10. In this case, an inner ring 72 havingthe outboard inner raceway 27 is fitted onto the outside periphery ofthe hub ring 10, and axially one side (outboard side in this embodiment)of the outer joint member 41 as the outside-diameter side member isbutted through an inner ring 72 against a face positioned in a radialdirection of the hub ring 10 as the inside-diameter side member.Further, with an end face (bottom of the mouth portion 46, for example)of the axially other side (inboard side in this embodiment) of the outerjoint member 41 being supported by a receive member (not shown), theswaging jig 54 is pushed toward the axially other side into the insideof the hub ring 10. Thus the swaging jig 54 is pressed against theportion 34 to be swaged, and the effect similar to that described abovecan be obtained.

In the embodiment in FIG. 28, the inner ring 72 having the inner raceway27 is fitted onto the hub ring 10; however, the inner ring 72 can alsobe fitted onto a portion extended outboard from the cylindrical portion41 a of the outer joint member 41 (figure showing the state is omitted).

FIGS. 30 and 31 show another example of the swaging jig 54 that isexpandable and reducible in diameter as the case shown in FIG. 12. Theswaging jig 54 of this example is particularly suitable for a case wherethe inner member 29 is of a bottomed cylindrical shape, or for example,as shown in FIG. 29, a case where a bottom of the mouth portion 46 ofthe outer joint member 41 in the embodiment in FIG. 1 is closed.

This swaging jig 54 is composed of the divided punch 55 divided at aplurality of positions in a circumferential direction and the insertionmember 56 slidably inserted into the inside of the divided punches 55.The divided punch 55 and the insertion member 56 are taper-fittedtogether through tapered faces 55 a and 56 a formed at the punch and themember, respectively. They are combined such that one of the taperedfaces guides the other tapered face in accordance with movement in theaxial direction of the insertion member, thereby the divided punch 55 isexpanded or reduced in diameter. The divided punch 55 is alwaysenergized to a diameter-reduction side with means such as an elasticmember.

A swaging process using this swaging jig 54 can be carried out in theprocedure described below. First, the swaging jig 54 is inserted from anopening side of the inner member 29, or, in this embodiment, from anopening side of the stem portion 45 of the outer joint member 41. Atthis time, the swaging jig 54 is kept in a reduced-diameter state sothat a diameter of the maximum outside-diameter portion 57 of theswaging jig 54 is smaller than the inside diameter of the portion 34 tobe swaged provided at an opening portion of the stem portion 45.Immediately after the maximum outside-diameter portion 57 has passed theportion 34 to be swaged, the swaging jig 54 is expanded to a diameterlarger than the inside diameter of the portion 34 to be swaged (FIG.29). After that, the swaging jig 54 is drawn in a direction opposite tothe insertion direction so that the maximum outside diameter portion 57that is expanded is pressed against the portion 34 to be swaged. Whenthe swaging jig 54 is drawn from the inside of the stem portion 45, withthe effect same as above, joining by swaging between the hub ring 10 andthe outer point member 41 and preload setting by compression strainproduced in the vicinity of the butt portion 70 are completed at thesame time.

Described above is a case as an example in which the inner raceway 27 or28 is provided at the outside-diameter side member (the hub ring 10 inFIGS. 1, 5, 27, and 29, the inner ring 35 in FIGS. 8, 18, 19, and 26,the outer joint member 41 in FIGS. 5, 7, and 28, and the second innerring 63 in FIG. 24); however, a member without an inner raceway can alsobe used as the outside-diameter side member.

Such a case is shown in FIG. 32 as an example. The figure shows that aportion facing to the portion 34 to be swaged of the second inner ring63 in the wheel bearing device according to the embodiment in FIG. 24 isseparated from the second inner ring 63 as a separate member (a ringmember 71). In this case as well, same as the case described above,axially one side (outboard side in this embodiment) of the ring member71 as the outside-diameter side member is indirectly butted against thefirst inner ring 61 (inside-diameter side member) through the secondinner ring 63. Further, the portion 34 to be swaged of the first innerring 61 is expanded in diameter while being pressed by the swaging jig54 toward the axially other side with the axially other side (inboardside) of the ring member 71 being supported by a support member (notshown). Thereby the joining by swaging of the inner ring 61 to the ringmember 71 and preload setting are made at the same time. In this case,deformation of the inner raceway 28 caused by swaging can be securelyprevented, because the inboard inner raceway 28 is formed on a separatemember from the outside-diameter side member (the ring member 71).

In a wheel bearing device according to the invention, since a lowhardness portion is expanded in diameter to make a hardened irregularportion bite into the low hardness portion, a solid joining is achievedat the fit portion between an inside-diameter side member and anoutside-diameter side member for preventing loosening of the joiningbetween both the members. Further, a low hardness portion having ahardness lower than that of the irregular portion is provided at aninside-diameter side member that is a separate member from anoutside-diameter side member having the irregular portion. It isarranged such that this low hardness portion is expanded in diameter, sothat the irregular portion can be sufficiently hardened while a largeexpansion allowance is secured at the low hardness portion and swagingcracks are prevented from being produced. Accordingly, the low hardnessportion can be made to deeply bite into the irregular portion to firmlyjoin both the members together.

Further, according to the invention, preload can be put to the inside ofthe bearing with an axial bearing clearance being negativesimultaneously when the joining by swaging of the inside-diameter sidemember and the outside-diameter side member is completed. Also, preloadcontrol is facilitated because an appropriate amount of preload can begiven only by the control of force applied by the swaging jig.

While there has been described what are at present considered to bepreferred embodiments of the invention, it will be understood thatvarious modifications may be made thereto, and it is intended that theappended claims cover all such modifications as fall within the truespirit and scope of the invention.

What is claimed is:
 1. A wheel bearing device in which a hub ring, aconstant velocity universal joint and a bearing are unitized together,the hub ring and an outer joint member of the constant velocityuniversal joint are fitted together, and, of inner raceways in doublerows of the bearing, one of the inner raceways is formed at the hub ringwhile the other inner raceway is formed at the outer joint member,wherein a hardened irregular portion is formed at an outside-diameterside member at a fit portion where the hub ring and the outer jointmember are fitted together while a low hardness portion having ahardness lower than that of the irregular portion is provided at aninside-diameter side member, and the hub ring and the outer joint memberare unitized together through expansion in diameter of the low hardnessportion to make the low hardness portion bite into the irregularportion.
 2. The wheel bearing device according to claim 1, wherein theoutside-diameter side member at the fit portion is the hub ring and theinside-diameter side member is the outer joint member.
 3. The wheelbearing device according to claim 1, wherein the outside-diameter sidemember at the fit portion is the outer joint member and the member atthe inner-diameter side is the hub ring.
 4. A wheel bearing device inwhich a hub ring and a bearing are unitized together, the hub ring andan inner ring of the bearing are fitted together, and, of inner racewaysin double rows of the bearing, one of the inner raceways is formed atthe hub ring while the other inner raceway is formed at the inner ring,wherein a hardened irregular portion is formed at an outside-diameterside member at the fit portion of the hub ring and the inner ring whilea low hardness portion having a hardness lower than that of theirregular portion is provided at an inside-diameter side member, and thehub ring and the inner ring are unitized together through expansion indiameter of the low hardness portion to make the low hardness portionbite into the irregular portion.
 5. The wheel bearing device accordingto claim 4, wherein the outside-diameter side member at the fit portionis the inner ring and the inside-diameter side member is the hub ring.6. The wheel bearing device according to claim 4, wherein an outer jointmember of a constant velocity universal joint is fitted to an insideperiphery of the hub ring in a manner in which torque is transmittable.7. The wheel bearing device according to claim 5, wherein an outer jointmember of a constant velocity universal joint is fitted to an insideperiphery of the hub ring in a manner in which torque is transmittable.8. The wheel bearing device according to claim 6, wherein a pilotportion that controls a clearance between the inside periphery of thehub ring and an outside periphery of the outer joint member is providednear a line extended from a line defining a contact angle formed byrolling members rolling on an inner raceway of the inner ring.
 9. Thewheel bearing device according to any one of claims 1 to 8, wherein thelow hardness portion is expanded in diameter at an inside-diameter sideof an area containing at least a part of either of the inner raceways.10. The wheel bearing device according to any one of claims 1 to 8,wherein the irregular portion is hardened with an induction heattreatment.
 11. The wheel bearing device according to any one of claims 1to 8, wherein the difference in hardness between the irregular portionand the low hardness portion is set at HRc 30 or more.
 12. The wheelbearing device according to any one of claims 1 to 8, wherein theirregular portion is formed with processes including broaching.
 13. Thewheel bearing device according to any one of claim 12, wherein theirregular portion is formed by a plurality of times of helicalbroaching.
 14. The wheel bearing device according to claim 1 or 4,wherein the irregular portion is formed with grooves in a plurality ofrows made to cross each other.
 15. A method of manufacturing the wheelbearing device according to either one of claim 1 or 4, wherein the lowhardness portion is expanded in diameter and a swaging jig, having adiameter larger than an inside diameter of the inside-diameter sidemember, slides on an inside periphery of the inside-diameter sidemember.
 16. The method of manufacturing the wheel bearing deviceaccording to claim 15, wherein the low hardness portion is expanded indiameter by the inside-diameter side member while the inside-diametermember is being pressed by the swaging jig in a direction where an axialbearing clearance is reduced.